The field of augmented reality is concerned with enhancing what we see and hear around us in the physical world. Researchers in this field superimpose computer graphics onto our view of real world objects. This enhances both our perceptions and our interactions with the real world. It enables improved performance of real world tasks.
There are multiple methods for achieving augmented reality. One method of providing an augmented view of the world is through the use of an LCD-screen based personal digital assistant (PDA). That technique has some drawbacks. The physical size of a PDA limits the information that can be presented to the user, regardless of future improvements in pixel resolution. The information displayed on a PDA is in the coordinate frame of the camera, not the user's own viewpoint. Use of a PDA requires the user to context-switch between the physical environment and the display. A PDA must be kept either on the user's person or nearby, but easily visible. A PDA only provides augmentation to an individual, or at best a small group of people clustered around a very small device.
Another method of providing an augmented view of the world is through the use of ‘see-through’ video micro-display eyeglasses. A drawback is that the tight coupling between the user's eyes coordinate frame and the displayed image coordinate frame requires very accurate processing of user head motion, e.g., a user head rotation must be accurately matched by a complementary rotation in the displayed image. Also, video micro-display eyeglasses are for individual use only, not shared use. Because the display is only a centimeter or so from the eye, working with an augmented object is awkward because other objects, such as the user's hands, can easily occlude the augmentation. Finally, fatigue factors of eye-worn displays are well known.
Projector-based augmented reality projects augmentation directly onto the physical scene. It decouples the user coordinate frame from the relationship between the projector and the physical object. One advantage of this is that there is no need for the difficult task of determining user head motion when showing projected information.
A rotating movie camera has been used to acquire a film of a living room, replete with furniture, and people. The room and furniture were then painted a neutral white, and the film was projected back onto the walls and furniture using a rotating projector that was precisely registered with the original camera, see Naimark, “Displacements,” Exhibit at the San Francisco Museum of Modern Art, San Francisco, Calif. 1984. This crucial co-location of the acquiring camera and displaying projector is common to most systems that use pre-recorded images, or image sequences to illuminate physical objects.
A projector and fiber-optic bundle have been used to animate the head of a fictional fortuneteller inside a real crystal ball, see U.S. Pat. No. 4,978,216 “Figure with back projected image using fiber optics” issued to Liljegren, et al., Dec. 18, 1990. Slides of modified photographs augmented with fine details have been used with very bright projectors to render imagery on a very large architectural scale. A well-known modem realization of this idea is Le Son et Lumière on Chateau de Blois in the Loire Valley of France. In addition, this medium is now being used elsewhere around the world to illuminate large-scale structures such as bridges.
The “Luminous Room” project treats a co-located camera-projector pair as an I/O bulb to sense and project imagery onto flat surfaces in the real physical surroundings of a room or a designated workspace, see Underkoffler et al. “Emancipated pixels: Real-world graphics in the luminous room,” SIGGRAPH '99, pp. 385-392, 1999. Their main focus is interaction with the information via luminous and tangible interfaces. They recognized co-planar 2D physical objects, tracked the 2D positions and orientations in the plane, and projected light from overhead to reproduce the appropriate sunlight shadows.
All those systems render compelling visualizations. However, cumbersome alignment processes can take several hours, even for a single projector. Many similar systems are based on the notion of one or more environmental sensors assisting a processor, which can compute the Euclidean or affine relationships between projectors and displays. Without the centralized sensors, the projectors are unable to augment the target objects. Those systems require a fixed special relationship between the projectors and the augmented objects. Any movement of either part requires the system to be recalibrated. Furthermore, the fixed nature of the projectors in those systems dictates that only certain parts of the objects can be augmented.
Therefore, it is desired to provide a context aware projector that does not have the limitations and problems of the prior art systems.